The use of construction manager–general contractor (CM-GC) project delivery is gaining momentum with highway projects across the United States. This project delivery process is different from the traditional design–bid–build (D-B-B) process in that an agency works with one CM-GC to develop the construction cost. To ensure that agencies receive fair market value, many agencies employ an independent cost estimator (ICE) in lieu of competitive bidding. The findings of a research effort to explore ICE roles, responsibilities, and best practices within highway construction are presented. The findings were derived through a review of previous literature, current agency CM-GC ICE policies, surveys of 25 completed CM-GC projects, and in-depth interviews with highway agency officials on six of the projects. The six projects were selected for interviews from the set of completed projects to allow for cross-case comparison. Although multiple best practices are identified, the two key findings of the research are that the ICE should have construction experience and local knowledge and should be an involved team member throughout the design process. In summary, all of the reviewed agencies found the ICE role to be essential in establishing a competitive construction contract cost and thereby gaining value through early contractor involvement. Some agencies found that the ICE added value beyond the costing process as a team member throughout design, but this practice was not found to be universal across all projects studied.